ATLANTA — Americans may be too fat, but at least their cholesterol is low. For the first time in nearly 50 years, the average cholesterol level for U.S. adults is in the ideal range, the government reported Wednesday.

Results from a national survey that included blood tests found the total average cholesterol level dropped to 199 last year. Experts consider 200 and lower to be ideal.

The growing use of cholesterol-lowering pills in middle-aged and older people is believed to be a key reason for the improvement, experts said. When the survey began in 1960, the average cholesterol was at 222.

Americans have gotten much heavier since then, but they’ve been able to lower their cholesterol with powerful drugs that carry few, if any, side effects. High cholesterol can clog arteries and lead to heart disease.

Doctors groups have increasingly recommended more aggressive use of these drugs in patients seen to be at risk for heart disease. And screening has become common — two-thirds of men and three-fourths of women had been screened for high cholesterol in the previous five years, according to the Centers for Disease Control and Prevention.

The result is that cholesterol medications are the top-selling class of U.S. drugs, and sales have grown steadily from about $13 billion in 2002 to nearly $22 billion in 2006, according to IMS Health, a Connecticut-based consulting company that monitors pharmaceutical sales.

“There’s been an explosion in the use of these medications, and appropriately so in the majority of cases,” said Dr. Elizabeth Jackson, a preventive cardiologist at the University of Michigan Medical Center.

The CDC, which runs the cholesterol survey, collects data in two-year intervals. The new results are based on a national sample of about 4,500 people age 20 and older from 2005-06. The new level of 199 compares with 204 in 1999-2000.

Researchers also found that the percentage of adults with high cholesterol, 240 or higher, dropped to 16 percent, down from 20 percent in the early 1990s.

They also reported that the most pronounced declines were in men 40 and older and women 60 and older.

“These age groups are the ones most likely to be treated with medication,” said Susan Schober of the CDC’s National Center for Health Statistics and lead author of the report.

However, there was little change in cholesterol levels for other age groups, prompting some experts to suspect the news may not be all good.

“This is kind of incomplete information,” said Dr. Roger Blumenthal, a Johns Hopkins University cardiologist.

Total cholesterol is a summary of HDL, or “good” cholesterol, and LDL, “bad cholesterol, and a measure of triglycerides, a form of fat. Obesity rates in teens and young adults have been shooting up, and it’s possible they are experiencing gains in triglycerides and losses in beneficial cholesterol, said Blumenthal, who also is a spokesman for the American Heart Association.

“If you take away the people on medication, I don’t think there’s been as much of a meaningful improvement as we would like,” he said.

Among the best-known prescription drugs for lowering cholesterol are Lipitor, made by Pfizer Inc.; Zocor, by Merck & Co.; and Pravachol, from Bristol-Meyers Squibb.

Another is Mevacor, a product Merck hopes to begin selling over the counter. However, federal health officials worry that some consumers can’t be trusted to know whether it’s appropriate for them.

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